Subject (System) Boundary   A subject (system) boundary is a type of partition that represents the boundary between the thing you are representing with the use cases (inside the boundary) and the actors (outside the boundary). Its most typical usage is the boundary of an entire system. Use cases can be used to represent subsystems and classes and so the boundary may be more specific than an entire system. A package with a stereotype topLevel can be used as a boundary and name space within the use case model to denote the same thing as the use case boundary.

Explanation

A use case boundary is a type of partition that defines inside and outside regions; it is used to indicate what is outside an entity - the actors, and what is inside - the use cases. Use case boundaries are often omitted since they are implicit in the diagram.

Related Entries

Actor  Used Together An actor is related to a use case boundary in the sense that the actors are outside the boundary and the use cases lie inside the boundary. The perimeter of the boundary must by definition cut through the associations that relate actors to the use cases with which they communicate.

Use Case  Used Together A use case is related to a use case boundary in the sense that the use cases lie inside the boundary and the actors lie outside the boundary.